1. Technical Field
The present disclosure relates to a smart key system.
2. Description of Related Art
In the related art, there are known smart key systems that cause vehicle-mounted equipment to perform a predetermined operation (for example, locking or unlocking of a door, or the like) on the basis of transmission and reception of signals in both directions between a vehicle (vehicle-mounted device) and a portable device when a user carries a smart key (portable device). Specifically, in a smart key system as an example, a low-frequency request signal is transmitted from a vehicle (vehicle-mounted device), a portable device transmits a high-frequency response signal, a smart key is certified on the basis of the response signal received by the vehicle-mounted device, and vehicle-mounted equipment is made to perform a predetermined operation on the basis of a certification result.
In this smart key system, a technique of periodically switching the reception sensitivity of the request signal in the portable device between a predetermined normal sensitivity and a high sensitivity higher than this normal sensitivity is suggested (for example, refer to Japanese Patent Application Publication No. 2013-83051 (JP 2013-83051 A)).
According to the technique disclosed in JP 2013-83051 A, the reception sensitivity of the request signal can be periodically the high sensitivity. Therefore, the portable device can perform communication between the vehicle-mounted device and the portable device even in a case where a user is present out of an area where the request signal is receivable with the normal sensitivity. That is, a communicable distance when the request signal is transmitted from the vehicle-mounted device to the portable device (hereinafter simply referred to as a “communicable distance”) can be periodically extended.
For example, there is a case where the vehicle-mounted device determines that the user is apart from the vehicle by viewing a timing at which the response signal from the portable device is interrupted after a predetermined manipulation (closing reservation manipulation of an electric door, closing manipulation of a door, or the like) has been performed in the vehicle, and the vehicle-mounted equipment is made to perform the predetermined operation (the closing of the door, locking of the door, or the like). In this case, while the communicable distance remains normal, it becomes impossible for the portable device to receive the request signal when the user has been slightly apart from the vehicle. As a result, irrespective of the user is not sufficiently apart from the vehicle in practice, the vehicle-mounted device may determine that the user has been apart from the vehicle. In contrast, by extending the communicable distance, the portable device can receive the request signal from the vehicle-mounted device even if the portable device is at a position further apart from the vehicle. Therefore, the vehicle-mounted device can receive the response signal from the portable device until the user is sufficiently kept from the vehicle. For that reason, it is confirmed that the user has been sufficiently apart from the vehicle, so that the vehicle-mounted equipment can be made to perform the predetermined operation.